3 Eye-tracking during reading
What can we learn from the measures?
4 Eye-tracking
- in (psycho)linguistics
- during reading
- visual world paradigm
- in psychology
- pupillometry
- visual search
- but also
- market research
- diagnostic tool
4.1 Eye movements
- saccades: eye movements (e.g., from one word to another)
- average saccade legnth: 7-9 letters (in alphabetic writing systems)
- fixations: ‘looking at’ something, e.g., a word (little movement)
- when information is taken in
- average duration: 225-250ms (ranging 50-600ms)
- regressions: saccades to earlier text
- occurance: 10-15% of saccades in skilled readers
4.2 The eye-tracker
- eye-tracker
- camera \(+\) infrared illuminator
- screen
- chin/head rest
- in our lab: desk-mounted
5 Eye-tracking during reading
5.1 Eye-tracking reading measures
- inform theories of language processing via linking hypotheses
- linking visual attention to processing
- typically, we compare reading times as a function of some manipulation
- e.g., Sally went/goed to the store.
- longer reading times are taken to reflect processing costs, associated with e.g., sentence complexity or anomalies
5.2 Region of interest (ROI)
- can be anything on-screen
- sentence-level
- word/region-level
- a certain part of the screen
5.3 Measures (dependent variables)
- what we measure = dependent variables (usually…)
- their value depends on some predictor (e.g., word frequency)
- measures of duration (time spent on a region)
- first fixation
- first-pass reading time
- regression path duration
- total reading time
- data type: continuous
- measures of revisits
- number of fixations
- number of regressions in/out
- regression in/out (yes or no)
- probability of regressions in/out (0:1)
- data type: binary (0,1) or count
5.4 Independent variables
- what can influence reading measures? (Clifton & Staub, 2011; Juhasz & Pollatsek, 2011; Rayner & Liversedge, 2011; Warren, 2011)
- some examples:
- Word properties
- word frequency
- word length
- Sentence-level influences
- context (i.e., prediction)
- semantic or grammatical manipulations
- Inter- and intra-individual
- domain-specific expertise
- reading skill level
5.5 What do these measures tell us?
- eye-tracking during reading can tell use when and where processing costs are incurred
- early measures involve “first contact with a word” or region: first-fixation, first-pass reading time (Vasishth et al., 2013, p. 126)
- late measures involve regressions to a region: e.g., total reading time
- may also include ‘spillover’ effects from early processing
- eye-tracking during reading measures can therefore tell us about stages of processing